Single site or metallocene or constrained geometry type catalysts are well known. Typically such catalysts comprise a transition metal such as titanium, zirconium or hafnium having at least one group which is activated by a cocatalyst, such as a halide group or an alkyl or alkoxy radical, and at least one aromatic ligand such as cyclopentadienyl or indenyl which is typically bridged to another group such as another aromatic ligand or an amine.
Some polymerization techniques require a supported catalyst. Fairly early on it was found that metallocene type catalysts could be supported on inorganic supports which had reactive hydroxyl groups such as silica. The metallocene type catalyst was brought into contact with the surface of the support. The metallocene catalyst was either deposited upon or reacted with the support. An example of such is U.S. Pat. No. 4,701,432 issued Oct. 20, 1987 to Welborn, Jr. assigned to Exxon Chemical Patents Ltd. The Welborn patent suggests a direct reaction between the catalyst and the support surface and does not seem to contemplate any significant spacing between the metallocene catalyst and the support.
A further stage in the development of supported catalysts was the deposition or reaction of a metallocene catalyst with a support which contained a cocatalyst already supported on the surface. This could have been by adsorption or by reaction of a cocatalyst such as an aluminum alkyl or an aluminoxane with the support surface or by more interesting means such as generating aluminoxane in situ by reacting aluminum alkyls in the presence of small amounts of water. Representative of this type of art are U.S. Pat. No. 5,422,325 issued Jun. 6, 1995 and U.S. Pat. No. 5,616,665 issued Apr. 1, 1997 both in the name of Jejelowo et al, assigned to Exxon Chemical Patents, Inc. This art teaches an indirect support as the catalyst reacts with the aluminum compound deposited upon the support.
U.S. Pat. No. 5,202,398 issued Apr. 13, 1993 to Antberg et al, assigned to Hoechst Aktiengesellsdchaft teaches reacting a metallocene type catalyst with a support having reactive hydroxyl groups. The patent teaches that in the catalysts at least one of the aromatic rings is substituted with a radical terminating in a silyl ether. The ether is said to react with the surface hydroxyl groups of the supports and the catalyst becomes bound to the support through a bond between the oxygen on the support and the silicon in the now silyl terminated radical attached to an aromatic ligand in the metallocene catalyst. The resulting catalyst is said to be a metallocene catalyst "tethered" to but spaced distant from a support.
It is obvious from the teachings of U.S. Pat. No. 4,701,432 that this type of metallocene catalyst could also directly react with the hydroxylated support (via reaction of e.g. the ZrCl bond in a metallocene catalyst with surface OH groups) and the resulting supported, metallocene catalyst would not be "tethered" as described in U.S. Pat. No. 5,202,398.
U.S. Pat. No. 5,202,398 does not exemplify that such "tethered" metallocene catalysts are single-site, forming polymers with a narrow molecular weight distribution, as in the present invention. In fact, as exemplified in the present patent application, this patent leads to supported metallocene catalysts which are multi-site, producing polymers with a broad and multi-modal molecular weight distribution. U.S. Pat. No. 5,202,398 does not teach how a bridged metallocene catalyst can be "tethered" to a support in an optimal manner as described in the present invention. Finally, U.S. Pat. No. 5,202,398 does not describe the reaction processes of the present invention which are necessary to carry out the "tethering" reaction in an optimal manner.
U.S. Pat. No. 5,824,620 issued Oct. 20, 1998 assigned to Repsol Quimica S.A. teaches a similar catalyst to that of U.S. Pat. No. 5,202,398. The support is either hydroxylated or the hydroxylated support is treated with a silylating agent terminating in group selected from e.g. a hydroxyl, amino, or thiol group which reacts with a metallocene functionalized with e.g. a halogen atom. Again, such reactive groups on the support could react directly with the Zr--Cl bonds of the metallocene catalyst and the resulting supported, metallocene catalyst would not be "tethered" as described in U.S. Pat. No. 5,824,620. U.S. Pat. No. 5,824,620 does not teach how a bridged metallocene catalyst can be "tethered" to a support in an optimal manner as described in the present invention. Finally, U.S. Pat. No. 5,824,620 does not describe the reaction processes of the present invention which are necessary to carry out the "tethering" reaction in an optimal manner.